Method for pneumatically placing semi-fluid materials

ABSTRACT

Quick-setting concrete is applied to a work surface by air conveying wet concrete through a hose to a nozzle and air conveying a dry accelerator powder for the wet concrete through a separate hose into juncture with the stream of suspended wet concrete a predetermined distance back of the nozzle. A positive metering concrete pump meters the concrete into a T-intersection where compressed air entering through one side of the top of the T impinges at substantially right angles to the flow of wet concrete through the base of the T resulting in shearing off of discrete pieces of wet concrete which are conveyed through a hose attached to the other side of the T-intersection. The positive metering concrete pump is directly attached to a positive metering device for the accelerator powder so as to maintain the ratio of wet concrete to accelerator constant.

United States atent [191 Broadfoot p [111 3,758,034 Sept. 11, 1973METHOD FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS [76] Inventor:John T. Broadfoot, 12714 Aurora Ave. N., Seattle, Wash. 98133 [22]Filed: Aug. 27, 1971 [21] Appl. No.: 175,462

Related US. Application Data [62] Division of Ser. No. 47,538, June 18,I970,

abandoned.

[52] US. Cl. 239/9 [51] Int. Cl. A62c' 1/12 [58] Field of Search 239/8,9

[56] I References Cited UNITED STATES PATENTS 3,077,415 2/1963 Ayres239/9 Primary Examiner-Lloyd L. King Attorney-Seed, Berry, Dowi'ey t kCross [5 7] ABSTRACT Quick-setting concrete is applied to a work surfaceby air conveying wet concrete through a hose to a nozzle and airconveying a dry accelerator powder for the wet concrete through aseparate hose into juncture with the stream of suspended wet concrete :apredetermined distance back of the nozzle. A positive metering concretepump meters the concrete into a T-intersection where compressed airentering through one side of the top of theT impinges at substantiallyright angles to the flow of wet concrete through the base of the Tresulting in shearing off. of discrete pieces of wet concrete which areconveyed through a hose attached to the other side of theT-intersection. The positive metering concrete pump is directly attachedto a positive metering device for the accelerator powder so as tomaintain the ratio of wet concrete to accelerator constant.

7 Claims, 4 Drawing Figures PAIENIEnsm um SHEET 1 BF 2 JOHN T.BROIQDFOOT VENT OR; I

PAIENIEUSEH mm 3,758,034

SHEEI 2 BF 2 JOHN T- BROADFOOT INVENTOR.

METHOD FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS This applicationis a division of Ser. No. 47,538, filed June 18, 1970, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an apparatus and method for metering, conveying and applyingwet concrete or other semi-fluid materials to a work surface, thesemifluid material having a quick-setting additive or accelerator addedthereto just prior to application to the work area. i

2. Prior Art Relating to the Disclosure Quick-setting additives forconcrete which provide an initial setting of the concrete in a matter ofseconds have, of recent, become available. These additives have beenadded in dry form to a dry concrete mix which is then applied to a workarea by means of a nozzle through which water in controlled amounts isdirected. Such a process is very useful in providing ground support inmines and tunnels, thereby replacing the conventional timer and steelsupports, and in repairing concrete structures, sewer lines, buildingretaining walls, water lines, etc.

Two basic methods of pneumatically placing concrete have been used, thedry method and the wet method. By the dry method, measured amounts ofcement, sand and aggregate are mixed dry and forced by compressed airthrough a hose to a nozzle where water is introduced into the drymixture before ejection from the nozzle. The principal disadvantage ofthe dry method is the lack of adequate control of the amount of wateradded to the dry mixture. The amount of water used is critical toobtaining optimum concrete. The amount of water is controlled generallybythe nozzle operator during application. His judgement, or the lack ofit, is the criteria used and the results generally obtained are lessthanoptimum. In addition to this disad- 2 added to the concrete mixbefore ejection from the nozzle using one of the True Gun-All machinesit is impossible to get uniform distribution of the accelerator due tothe erratic flow of wet concrete. The True Gun- All machine utilizes acylindrical air pressurized mixing drum in which multiple paddle wheelsrotate, each of the paddles having wiping blades thereon which contactthe inner surface of the drum. Alternate slugs" or measured amounts ofwet concrete and compressed air vantage the dry process requires thatthe sand used be pre-dried, thus limiting use of the process to periodsof good weather.

The so-called wet method utilizes a mixture of measured water andweighed amounts of cement, sand and aggregate. By adding a measuredamount of water to the dry mix'before application the quality anduniformity of the concrete can be closely controlled. Rebound, definedas the amount of material sloughing off the surface applied duringapplication, is reduced. One of the main problems encountered in the wetmethod is finding a way of transferring the wet concrete mixture fromthe mixing station through a hose or other conduit to the nozzle. Whenapplying concrete pneumatically it is desirable to use concrete mixeshaving a minim um of water (a stiff consistency) in order to promotequicker setting and reduced rebound. Such mixes are very difficult toconvey through a hose because of their frictional resistance to passagethrough a hose. Machines for pneumatically placing wet concrete areknown, such as the True Gun-All" machine manufactured by the DetroitTool Engineering Company of Lebanon, Mo. This'machine is incapable ofsmooth delivery of material and requires a high degree of maintenance.The amount of rebound is greatly affected by the flow of the material.When the flow of the material is uneven the rebound is significantlygreater. Additionally, when a quick-setting additive or accelerator isfrom a source other than the interior of the tank are produced, thecompressed air forcing the slugs of concrete through a hose to a nozzle.

Another means of conveying and spraying wet cementitious materials isdisclosed in U.S. Pat. No. 3,212,759 which utilizes a pressurized tankholding the concrete, the tank having therein aereating means foruniformly dispersing high pressure air in the form of small bubbleswithin the mass of cementitious material to decrease its internalfriction and facilitate delivery through a hose or a conduit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of theoverall apparatus of this invention which includes a positive meteringfluid pump, a metering device for an accelerator powder for the pumpedfluid, means connecting the fluid pump and the metering device directlytogether, and conduit means for delivering the mixed fluid andaccelerator out a common nozzle;

FIG. 2 is a cross-sectional view along section line 2-2 of FIG. 1;

FIG. 3 is a partial cross-sectional view along section line 3-3 of FIG.'2 illustrating the agitation means within the holding vessel for theaccelerator; and

FIG. 4 is a cross-sectional view of the T-section into which the fluidis metered by the fluid pump and in which compressed air is impingedagainst the fluid at substantially right angles thereto. i

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. '1,the overall apparatus of this invention comprises aframe or base support1 on which is mounted a fluid pump 10, a supply hopper for the pump 20,and a metering means for an accelerator powder 30.

Fluid pumps capable of efficiently handling fluids of heavy consistencyin which solids are entrained and which deliver a relatively smooth flowof the fluid are the type used in this invention. The pump is preferablyof the type wherein the fluid to be pumped is com: pletely isolated fromthe moving parts of the pump. A preferred type of pump for the heavyfluids used in this invention, particularly concrete in which rock oraggregate up to one inch in diameter is included, is described in U.S.Pat. No. 3,180,272 which is hereby incorporated by -reference. Asdescribed, fluid pumps of this type comprise a housing 11 comprised of acylindrical shell with headers bolted thereto as closures for the openends thereof. Each of the headers have a centrally located aperture toaccommodate a rotary shaft. Air seals surround the shaft within theapparatus in the outer end walls. Entry and exit ports are provided inthe cylindrical housing for a deformable or flexible hose to be receivedtherethrough, the hose extending about and bearing against the interiorsurface of the cylindrical housing. One of the ports serves as the entryport for the material to be pumped with the other port serving as theexit port. Only the exit port 12 is shown in FIG. 1. Within the housingand mounted on the shaft is a power driven rotor means which squeezesthe hose section within the cylindrical ring in repeating cyclesstarting at the entry end and working progressively towards the exitend. While the particular pump shown in the patent mentioned aboveutilizes two opposed elastic tires mounted for oribital travel aroundthe center of the cylindrical housing, other rotor designs may beemployed. if desired, only one elastic tire centrally mounted around theshaft may be used, or four elastic tires arranged at right angles toeach other in pairs using the planetary arrangement shown in the patentmay be used.

Pumps of the type shown in the above mentioned patent are capable ofefficiently pumping heavy fluids containing aggregate ranging in size upto 1 inch in diameter. The shaft of the pump is connected to a suit ablepower means (not shown). In FIG. 1, a shield is shown shielding the beltdriving the shaft of the concrete pump for safety reasons.

In front of the fluid pump and mounted on the same base support is afeed trough 20 in which cement and sand or cement, sand and aggregateare mixed prior to being pumped. The entry port of the pump communicateswith the trough 20. The feed trough 20 includes several rotor blades 21mounted on a shaft 22 running through the trough, the shaft being drivenby suitable power means (not shown). The rotor blades 21 thoroughly mixpredetermined amounts .of wet concrete made up of water, sand andcement, or water, sand, cement and aggregate. v

Directly connected to the fluid pump is a metering device 30 formetering predetermined amounts of a dry accelerator powder into theconduit for the wet concrete for quick setting thereof. The meteringdevice comprises a cylindrical holding vessel 31 for the acceleratorpowder supported on a base support 32 by legs 33. The holding vessel hasa bottom wall which tapers to an opening of smaller diameter than thecylindrical holding vessel. The opening in the bottom of the holdingvessel communicates with an opening in the side wall of conduit 34running horizontally to the vertically disposed holding. vessel. Withinconduit 34 is mounted a feed screw 35 rigidly attached to shaft 36 onwhich is mounted a variable speed pulley 37. Around the pulley istrained a belt 38 which is connected to the power means powering thefluid pump. A second pulley 39 around which belt 49 is trained, runs anagitator assembly to be described. The agitator assembly is shown incross-section in FIG. 2 and comprises a shaft 41 extending horizontallyand transversely through the holding vessel 31. The shaft has two ormore eccentric portions 42 on which are mounted section of chains 43which, as shaft is rotated, more vertically upwardly and downwardly toagitate the dry accelerator powder in the vessel. Also mounted on shaft41 are one or more blades 44 which aid in maintaining the acceleratorpowder in a free flowing state. The holding vessel 31 is constructed sothat it can be pressurized. The top of the holding vessel is fitted witha funnel 45 which aids in filling the vessel with the acceleratorpowder. The vessel is sealed with a domed closure 45 which seals aroundthe top opening. The closure 46 is'opened and closed by shaft 47. Asmall diameter valved conduit 48 communicating with the interior of thevessel 31 is provided to bleed off pressure in vessel 31 when refillingis necessary. The accelerator powder should be substantially free ofmoisture to achieve optimum results.

A conduit 50 is secured to the exit port of the concrete pump andextends to a T-section 51. The T- section 51 comprises a base portion 52secured to the discharge opening of the conduit 50 through which fluidis to be pumped and a top section 53 through one end of which compressedair is fed through conduit 54.

Semi-fluids of stifl consistency, such as a so-called dry concretemixture, (one which has a minimum of water added thereto), are verydifficult to pump any distance because of the high friction ofresistance of the material against the internal walls of the hose orconduit through which they are pumped. It is a decided advantage of thisinvention that wet concrete of heavy consistency, that is wet concretehaving a minimum of water therein, can be pumped distances greater than200 feet without difficulty. This is accomplished by metering the wetconcrete sections of the concrete with compressed air entering the topof the T-section through conduit 54. The compressed air impinges on thewet concrete being extruded into the T-s'ection by the fluid pump andcarries it through conduit 55 to nozzle from which it is sprayed onto awork surface. The pressure of the compressed air needed to force theconcrete through the conduit 55 can be regulated as desired. Thedischarge end of conduit 50 has an internal diameter about 3 inches asshown in FIG. 1 and the base of the T-section has an internal diameterof about the same. The conduit55 leading from the T-section of thenozzle shown in FIG. 1 has an internal diameter of about 2 inches.Though the diameter is reduced from 3 to 2 inches there has been nodifficulty in conveying the concrete for distances over 200 feet andupto 300 feet. Compressed air at about 60 psi has been used although thiscan be varied as desired. Because the air stream is moving the concretethrough the 2 inch line, the fluid pump becomes a metering machinehaving a maximum back pressure of about psi. The fluid pump delivers thewet concrete into the T-section in short sticks of material per rotorturn. The compressed air, however, exerts an elongating effect on thewet concrete resulting in a smooth metered feed at the nozzle.

The accelerator powder is introduced into the wet concrete throughconduit 56 which intersects conduit 55 at an angle a predetermineddistance back of nozzle 60. The accelerator powder is fed into conduit56 by feed screw 35 and is air suspended by. compressed air comingthrough conduit 56 at substantially right angles to the feed of theaccelerator powder. The air suspended accelerator powder mixes with thewet concrete coming through conduit 55 at the intersection of conduits55 and 56. The point of mixing of the accelerator and wet concretedepends upon the kind and amount of accelerator used, the consistency ofthe concrete and other factors. The distance may be from 3 to 10 feetback of the nozzle and preferably a distance of about 6 feet.

The amount of accelerator powder delivered into juncture with the wetconcrete is directly and accurately controlled by directly connectingthe metering device for the accelerator powder to the fluid pump.Preferably an amount of accelerator powder ranging from 2 to 8 percentby weight of the cement content of the concrete is used. The variablebelt speed control connected to pulley 37 enables varying amounts ofaccelerator powder to be mixed with the wet concrete prior to expulsionof the concrete from the nozzle. The optimum amount of acceleratorneeded for a particular application can be ascertained by one skilled inthe art. There are a number of accelerator powders for wet concretecommercially available any any of these may be used. l

The overall system comprises a positive metering concrete pump to whichis directly powered a positive metering dry accelerator feed. Theconcrete is conveyed by air through a hose and the powered acceleratoris conveyed by air through a separate hose into juncture with theconcrete hose a predetermined distance before issuing from the nozzle,preferably around 6 feet. The positive metering of the wet concrete intothe air stream gives a very smooth feed at the nozzle and gooddistribution of the accelerator within the concrete mixture.

Utilizing the apparatus shown in FIG. 1, concrete containing aggregateup to one inch in diameter has been conveyed up to 200 feet withmaintenance of good volume feed. A sand-cement mix has been conveyedover 300 feet. The concrete mixers which have been conveyed with theapparatus of this invention have consisted of about 40 percent rock oraggregate and 60 percent building sand, theaggregate having an averagesize of about /8 inch in diameter. Rebound is very much reduced with theapparatus of this invention over that accomplished by the prior art.Application rates are higher than machines of the prior art, ranging upto 10 cubic yards per hour. The material is so quick setting that 12inch knobs of material have been built up on vertical surfaces withoutsloughing. The concrete setsso quickly that even when water is flowingthrough an opening to be covered with concrete the hole can becoveredwithout the water affecting it. For example, in a tunnel throughwhich a full flow ,of water flowing, a concrete mixture was sprayed. Theconcrete completely sealed off the opening through which the water wasrunning without difficulty. The machine and method of this inventionoffer advantages over those known in the prior art in (l higherproduction, (2) less dust, (3) less skill required by the operator ofthe nozzle as he does not have to control and observe rebound of theconcretebeing applied, (4) precontrol of water content of the concretemixture, allowing optimum water content and ininimumrebound, (5) nomoisture control of the sand, (6) versatility of the apparatus (that is,it can be used for pressure grouting or for various other applications)and (7) easy maintenance and easy clean-up. No build-up of material ineither the mixing equipment or the nozzle was noted during operationover fairly long periods of time. The pump and line are easily cleaned.The mixing equipment needs only to be washedout. No build-up in the last6 feet of delivery hose was experienced in spite of the addition ofaccelerator to the wet concrete at a point 6 feet back of the nozzle.Another advantage of the machine of this invention is the ability toturn the accelerator on and off at will while applying the concrete. Theaccelerator powder usedin most applications is expensive and it ishighly desirable to be able to control the amount of ac celerator usedto minimize expense.

I claim:

l. A method of applying a concrete slurry incorporating a quick-settingadditive to a work surface, the slurry setting to a hard concreteproduct within seconds after application, comprising:

metering, under pressure, a concrete slurry having a controlled amountof water added thereto to a discharge zone, conveying the slurry fromthe discharge zone to a discharge nozzle, pneumatically metering andconveyinga dry, particulate, quick-setting additive for the concreteslurry into the concrete slurry stream before ejection of the slurryfrom the discharge nozzle, the additive uniformly mixing with theconcrete slurry before discharge from the nozzle. 2. A method ofapplying a concrete slurry incorporating a quick-setting additive to awork surface, the slurry setting to a hard concrete product withinseconds after application, comprising:

metering, under pressure, a predetermined amount of a concrete slurryhaving a controlled amount of water added thereto to a discharge zone,impinging a compressedgas against the stream of concrete slurry enteringthe discharge zone at a pressure sufficient to shear discrete pieces ofthe concrete slurry and suspend them in the gaseous stream for conveyingthrough a conduit to a discharge nozzle, and suspending a dry,particulate, quick-setting additive for the concrete slurry in a streamof compressed gas, the gas stream conveying theadditive through aconduit into the concrete slurry stream before ejection of the concreteslurry mixture from the discharge nozzle onto the work surface, theadditive uniformly mixing with the suspended concrete slurry.

3. The method of claim 2 including controlling the weight ratio ofconcrete slurry to quick-setting additive.

4. The method of claim 3 wherein 2 to 8 percent by weight ofquick-setting additive is added to the concrete slurry based on theweight of the cement in the concrete slurry.

5. The method of claim 3 wherein the quick-setting additive is mixedwith the concrete slurry at a point ranging from 3 to 10 feetbeforeejection of the concrete slurry from the discharge nozzle.

6. The method of claim 1 wherein the concrete slurry is metered underpressure by (1) admitting a concrete slurry in a compressible hosehaving inlet and outlet ports at the respective ends thereof, (2)compressing the hose beginning at the inlet port: and moving toward theoutlet port to move a pocket of the concrete slurry contained thereinprogressively from the inlet port through the outlet port to thedischarge zone.

7. A method of applying a concrete slurry incorporating a quick-settingadditive to a work surface with setting of the concrete slurry-additivemixture to a hard end product within seconds after application,comprising:

admitting a concrete slurry into a compressible hose having inlet andoutlet ports in the respective ends thereof,

comprssing the hose beginning at the inlet port and moving toward theoutlet port to move a pocket of the concrete slurry contained thereinprogressively from the inlet port through the outlet port to a dischargezone,

and

conveying the additive suspended in the gas stream into the suspendedstream of concrete slurry before ejection of the slurry-additive mixturefrom the discharge nozzle onto the work surface, the additive uniformlymixing with the suspended concrete slurry before discharge from thenozzle.

1. A method of applying a concrete slurry incorporating a quicksettingadditive to a work surface, the slurry setting to a hard concreteproduct within seconds after application, comprising: metering, underpressure, a concrete slurry having a controlled amount of water addedthereto to a discharge zone, conveying the slurry from the dischargezone to a discharge nozzle, pneumatically metering and conveying a dry,particulate, quicksetting additive for the concrete slurry into theconcrete slurry stream before ejection of the slurry from the dischargenozzle, the additive uniformly mixing with the concrete slurry beforedischarge from the nozzle.
 2. A method of applying a concrete slurryincorporating a quick-setting additive to a work surface, the slurrysetting to a hard concrete product within seconds after application,comprising: metering, under pressure, a predetermined amount of aconcrete slurry having a controlled amount of water added thereto to adischarge zone, impinging a compressed gas against the stream ofconcrete slurry entering the discharge zone at a pressure sufficient toshear discrete pieces of the concrete slurry and suspend them in thegaseous stream for conveying through a conduit to a discharge nozzle,and suspending a dry, particulate, quick-setting additive for theconcrete slurry in a stream of compressed gas, the gas stream conveyingthe additive through a conduit into the concrete slurry stream beforeejection of the concrete slurry mixture from the dischArge nozzle ontothe work surface, the additive uniformly mixing with the suspendedconcrete slurry.
 3. The method of claim 2 including controlling theweight ratio of concrete slurry to quick-setting additive.
 4. The methodof claim 3 wherein 2 to 8 percent by weight of quick-setting additive isadded to the concrete slurry based on the weight of the cement in theconcrete slurry.
 5. The method of claim 3 wherein the quick-settingadditive is mixed with the concrete slurry at a point ranging from 3 to10 feet before ejection of the concrete slurry from the dischargenozzle.
 6. The method of claim 1 wherein the concrete slurry is meteredunder pressure by (1) admitting a concrete slurry in a compressible hosehaving inlet and outlet ports at the respective ends thereof, (2)compressing the hose beginning at the inlet port and moving toward theoutlet port to move a pocket of the concrete slurry contained thereinprogressively from the inlet port through the outlet port to thedischarge zone.
 7. A method of applying a concrete slurry incorporatinga quick-setting additive to a work surface with setting of the concreteslurry-additive mixture to a hard end product within seconds afterapplication, comprising: admitting a concrete slurry into a compressiblehose having inlet and outlet ports in the respective ends thereof,comprssing the hose beginning at the inlet port and moving toward theoutlet port to move a pocket of the concrete slurry contained thereinprogressively from the inlet port through the outlet port to a dischargezone, impinging a compressed gas against the stream of concrete slurryentering the discharge zone at a pressure sufficient to shear discretepieces of concrete slurry from the mass entering the discharge zone andsuspend them in the gaseous stream for conveyance through a conduit to adischarge nozzle, suspending a dry, particulate, quick-setting additivefor the concrete slurry in a compressed gas stream, and conveying theadditive suspended in the gas stream into the suspended stream ofconcrete slurry before ejection of the slurry-additive mixture from thedischarge nozzle onto the work surface, the additive uniformly mixingwith the suspended concrete slurry before discharge from the nozzle.